With ever increasing demand for aviation fuel to power our aeroplanes and its steep rising costs the time has come for us to find a more cost effective, efficient and ecofriendly way to power our aircrafts, thus solar powered aircrafts came into existence. The planes have photovoltaic cells on their wings which gather solar energy thereby recharging the batteries that powers its propellers. The planes are so designed that it can fly even during the night time and can stay in the air for as long as 26 hours.

Introduction and importance of solar powered aircrafts

Travelling by aeroplanes has been one of the most effective and efficient means of transportation, even now it is one of the most preferred means of transportation. Aviation fuel, the fuel which is used in aeroplanes is a fossil fuel whose reserves are depleting at an extremely fast rate and also the emissions caused by such aeroplanes using aviation fuel is affecting our environment as well as our ozone layer. So the time has come for us to power our aeroplanes using some other sources of energy and thus then emerged solar powered aeroplanes. One of the biggest advantage of using solar powered aircrafts is that there would be no emissions and also over the years in the long run the cost of travelling by air would reduce drastically. Over a considerable period of time these aircrafts have been modified and now these aeroplanes can fly around the world even without stopping once even during the night-time. These aircrafts have the capacity to stay in the air for as long as 26 hours. Thus if solar powered aircrafts are introduced on a large scale it will make our world a global village making air travel eco-friendly and extremely cheap. Solar powered aircrafts can also play a pioneering role in the development of the economy in developing countries like India where air travel is still out of the bounds for the poorer sections of the society. Thus we can say that introduction of solar powered aircrafts will usher in a revolution that might change the belief which the common man has about air travel.

How does the solar impulse aircraft work?
The aircraft uses super-efficient solar cells and batteries to stay in the air after the Sun's rays had faded. The plane has 12,000 solar cells arranged on its wingspan which collected enough energy to power the plane for the flight. There are 11,628 monocrystalline silicon cells, each 150 microns thick, they have been selected for their lightness, flexibility and efficiency. At? 22%, their energy efficiency
could have been higher, but the additional weight would have affected? the aircraft during night flight.

Currently ?the major constraint of the project is storing energy in the lithium polymer batteries. At the present stage, the maximum energy density is 220 Wh/kg. The accumulators which are required for the night flight weigh 400 kg, equal to ? of the total weight of the aircraft. Success is therefore possible only by maximizing aerodynamic performance and optimizing the energy chain.

What were the sources of energy?

At midday, each m? of land surface receives an equivalent of 1,000 watts, or 1.3 horsepower
of light power. Over 24 hours this averages to 250 W/m?. With 200m? of photovoltaic cells and 12% total efficiency of the propulsion chain, the aircraft?s engines achieve on average of 8 HP or 6 KW ?And it is? this energy which is ?optimized from the solar panel to the propeller by the efforts of the entire team of solar impulse.

How does the propulsion system work?

Beneath the wings of the solar impulse plane are four gondolas, each containing a 10 HP motor, a lithium polymer battery set and a management system controlling charge/discharge and temperature. The thermal insulation had been designed to conserve the heat radiated by the batteries and to keep them functioning even at -40?C which the plane will encounter ?at 8,500 metres. Each engine is fitted with a reducer that limits the rotation of each 3.5 metre diameter, twin-bladed propeller within the range of 200-4,000 rpm.

What is the solar impulse aircraft made of?

With a 63.40 m wingspan and with the necessary rigidity, lightness and flight controllability and ?just 1,600 kg take-off weight is a challenge that had never before been met in aeronautics. Solar Impulse is built round a carbon fibre-honeycomb composite using a sandwich structure. The upper wing surface is covered with a skin of encapsulated solar cells, and the undersides of the wings with a high resistance flexible film. 120 carbon fibre ribs placed at 50 cm intervals profile these two layers and give the body its aerodynamic shape.

Some technical details

Wingspan 63.40 m

Length 21.85 m

Height 6.40 m

Motor power 4 x 10 HP electric engines

Solar cells 11,628 (10,748 on the wing,880 on the horizontal stabilizer)

Average flying speed 70 km/h

Maximum altitude 8,500 m (27,900 ft)

Weight 1,600 kg

Take-off speed 35 km/h

Pressurized air cabin

Advanced on board auto pilot system

Advanced inbuilt onboard computers to conserve power

What is? the? economic potential? of? the project?
The project solar impulse has got tremendous economic potential. Some of its main partners include Omega, Deutsche bank and SOLVAY.? Planes like the solar impulse are the planes of the future, like any Boeing or Airbus this plane can stay in the air for as long as 26 hours and even fly during the night time, the only major difference between the solar impulse plane and any other commercial plane is that? it cannot carry too much weight. The research team of the solar impulse project is working hard to overcome this challenge they have also modified the aircraft in such a way that it can fly around the globe in 20-25 days.
According to Adrian Scott, a member of the research team, he says that once the plane is modified and made ready to carry heavy load and specially passengers this plane (solar impulse) will be one of the biggest competitors to Boeing and Airbus. He also added by saying that this plane(solar impulse) once fully modified and upgraded to the levels of any commercial plane will bring a revolution in the world of commercial jets as the solar impulse plane doesn?t require any aviation fuel to power itself and can fly in the air simply by charging itself from the energy gained from the sun?s light. He also said that in the years to come most of the commercial planes will be solar powered as these planes are not only fuel efficient but also have low maintenance costs. Thus we can say that the solar impulse project has got huge economic potential as in the years to come these are the planes which will become commercial jets of the future.